1. Field of the Invention
The present invention relates to Ta and Ti precursors useful in the formation of a Ta-based or Ti-based material on a substrate, and includes tantalum amide precursors for formation of tantalum nitride on a substrate, and methods of use of such precursors for forming TaN material, e.g., thin film layers of TaN, on a substrate. The invention also contemplates single source compounds for the formation of TaSiN or TiSiN material on a substrate.
2. Description of the Related Art
Copper is of great interest for use in metallization of VLSI microelectronic devices because of its low resistivity, low contact resistance, and ability to enhance device performance (relative to aluminum metallization) via reduction of RC time delays thereby producing faster microelectronic devices. Copper CVD processes which are suitable for large-scale manufacturing and the conformal filling of high aspect ratio inter-level vias in high density integrated circuits are extremely valuable to the electronics industry, and are therefore being extensively investigated in the art.
Although CVD of Cu is gaining momentum in the semiconductor manufacturing industry, several problems still inhibit the integration of copper metallurgy in such microelectronic device applications. In specific, CVD of a suitable diffusion barrier for the copper metallization must be available to ensure the long-term reliability of the copper-based metallurgy in integrated circuits (ICs).
TaN and TaSiN have been demonstrated as a suitable metal diffusion barrier. A CVD process of TaN would obviously be advantageous and is currently the focus of development efforts by semiconductor equipment manufacturers. The CVD of TaN is at present carried out using Ta(NMe.sub.2).sub.5, a solid source precursor, as the source reagent. However, Ta(NMe.sub.2).sub.5 is a solid, and given the limited volatility of Ta(NMe.sub.2).sub.5, new, robust and more volatile tantalum amide precursors are needed. The films deposited from such sources must be conducting, conformal and of high purity. It would be extremely advantageous to utilize a suitable liquid source reagent as a tantalum amide precursor. For example, an alternative TaN precursor is Ta(NEt.sub.2).sub.5, which is reportedly a liquid. However, this source reagent is unstable to elevated temperature conditions, readily decomposing to a tantalum imide species, Ta(NEt)(NEt.sub.2).sub.3, upon heating, and thereby is an unsatisfactory candidate as a liquid source reagent for TaN barrier layer formation.
TaSiN and TiSiN are also currently being investigated in the art as diffusion barriers. A CVD process for these ternary barrier layer materials would also be advantageous and also is the focus of development efforts in the field. The CVD of TaSiN is a present carried out using Ta(NMe.sub.2).sub.5 as the Ta source and silane as the silicon source. Further, TaCl.sub.5 in combination with silane and ammonia has been used to deposit TaSiN thin films. Apart from the hazards associated with handling a pyrophoric gas such as silane, the dual source reactor configuration required with such precursor species (TaCl.sub.5, Ta(NMe.sub.2).sub.5 and silane) also increases the cost and complexity of the semiconductor manufacturing operation.
Another approach to barrier layer formation entails the PVD and CVD deposition of high purity Ta metal on the silicon substrate. The resulting Ta layer will form TaSi.sub.x at the silicon contact region (i.e., the Ta bottom surface), and subsequent elevated temperature reaction of the Ta layer with a nitrogenous reactant such as NH.sub.3 or N.sub.2 will induce nitridation of the Ta top-surface. Thus, a TaSiN ternary diffusion barrier or a layers TaSi/TaN structure can be formed. This type of ternary diffusion barrier has been reported in the art and provides excellent contact resistance and diffusion barrier properties toward Cu metallization and integration of ferroelectric thin films.
In all instances of the formation of a Ta-based diffusion barrier, an effective CVD approach to conformally coat inter-level (&lt;0.15 .mu.m) vias and sidewalls is critical, and the CVD source reagent must be storage-stable, of appropriate volatility and vaporization characteristics, with good transport and deposition characteristics to produce a high-purity, electronic quality thin film.
There is a continuing and increasing need in the art for improved CVD source reagents for forming Ta-based diffusion barrier layers on microelectronic substrates, to facilitate copper metallization. Such CVD source reagents are desirably liquid in character, to facilitate their processibility using techniques such as liquid delivery CVD, wherein the liquid source reagent is rapidly vaporized, e.g., by flash vaporization on a heated element such as a grid, screen or porous metal body, to produce a volatilized source reagent. The resulting source reagent vapor can then be transported to the CVD chamber and contacted with a substrate maintained at appropriate elevated temperature, to effect the deposition on the substrate of the Ta-based material.
It therefore is an object of the present invention to provide useful precursor compositions for the formation of Ta-based material and Ti-based material on substrates.
It is another object of the invention to provide a method of forming a Ta-based material, such as TaN or TaSiN, or Ti-based material, such as TiN or TiSiN, on a substrate, using such precursor compositions.
Other objects and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.